In recent years, people pay more attention to ecological resources and scenery quality. Therefore, when public constructions, such as the construction of roads, river banks, landfill fields, retaining walls, etc., have connection with slope stabilization, vegetation, soil and water conservation and environmental conservation, it is a must the slope stabilization function and the safety in use be taken into consideration in these public constructions, so that natural, green and beautiful scenery can be created after the public constructions are completed. In the past, to avoid destruction of the ecological environment and adverse influences on the natural scenery at the construction sites, and to create natural scenery in harmony with the existing environment, the ecology and environment-related public constructions would usually adopt planting methods to green the construction sites, so as to create an environment in harmony with the nature.
In the conventional slope protection constructions, the riverbank protection constructions, and the soil and water conservation constructions, a netted vegetation blanket is spread on the earth surface after grass and plant seeds are sown or sprayed, and the netted vegetation blanket is further covered with soil. By doing so, plants and grass grown on the slopes are protected against undesirable wash-away by rainwater, and soil at the slopes is protected against erosion to ensure good soil and water conservation and greening of surrounding environment.
According to one of the conventional netted vegetation blankets, the blanket has three layers, including an upper grid layer, a middle fiber layer, and a lower grid layer. The conventional three-layer netted vegetation blanket has relatively low porosity, which prevents plant and grass seeds below the spread blanket from growing upward and passing through the blanket. Further, the conventional three-layer netted vegetation blanket has relatively loose layered structure, and the upper and lower grid layers are not a three-dimensional structure. As a result, the grass seeds sown or spray-planted below the blanket are easily washed away by rainwater during the construction. The poor vegetation effect in turn causes erosion of soil spread over the blanket. Further, the middle fiber layer is usually formed from natural fibers, which are subject to damage by worms to thereby weaken the overall structural strength of the netted vegetation blanket. Therefore, the conventional three-layer netted vegetation blanket requires improvement.
FIG. 1 shows another conventional netted vegetation blanket disclosed in Taiwan Patent Publication No. M249977, which is characterized in a blank blanket 10 woven from a low-shrinkage yarn, and a plurality of ribs 11 made of high-shrinkage yarns. The ribs 11 are axially extended to space from one another, and are provided on the same side of the blank blanket 10 by way of partially weaving onto the blank blanket 10. With the ribs 11 spaced on and partially woven to the blank blanket 10, a plurality of interwoven locations 12 and a plurality of non-interwoven locations 13 are formed on the blank blanket 10. The blank blanket 10 with the ribs 11 is then heated and the ribs 11 are shrunk to form a plurality of corrugations 14 on the blank blanket 10. The above netted vegetation blanket disclosed in Taiwan Patent Publication No. M249977 has the following major disadvantage: the corrugations 14 are formed by heating and shrinking the blank blanket 10 and the ribs 11, and have low flexibility and elasticity. It is preferable a netted vegetation blanket can be wound into roll form for convenient storage and transport and be stretched for use. However, the corrugations 14 will become deformed and no longer have a three-dimensional shape once the netted vegetation blanket is wound. The deformed corrugations 14 lose their intended function to thereby lower the performance and effect of the netted vegetation blanket. Moreover, with the fixedly shaped corrugations 14, the blanket wound into roll form would become too loose to be easily handled during transporting.
It is therefore desirable to develop an improved netted vegetation blanket to overcome the drawbacks in the conventional netted vegetation blankets.